Combined seat and backrest unit



FIG. 1 is a perspective view of a combined seat and backrest unit embodying my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a side elevation view thereof, showing the side opposite that shown in FIG. 1; and

FIG. 5 is a rear elevation view thereof. 

The ornamental design for a combined seat and backrest unit, as shown and described. 